Proliferative retinopathies were studied biochemically in an experimental model, using newborn and young dogs and cats. Studies involved the identification of vasoproliferative factor(s) and elucidation of vasoproliferation mechanism. The first phase of studies was focused on: (1) the relationship between age-dependent vitreous soluble protein patterns (both components and content) and normal vascularization and abnormal neovascularization in retina and (2) the bioassay technique to detect and measure the biological activity of vasoproliferative factor(s). In the latter, the modified rabbit cornea micropocket and the endothelial cell culture techniques have proven to be the most promising ones. Studies on the vitreous homogenate to date indicate that the vitreous soluble proteins may be fundamentally involved in the process of normal retinal vascularization. Studies are in progress to identify the vasoproliferative factor(s), with the eventual goal of purifying the factor(s). BIBLIOGRAPHIC REFERENCES: Components of Vitreous Soluble Proteins: Effect of Hyperoxia and Age, C.-H. Chen, and A. Patz, Invest. Ophthal., 15:228 (1976). The Stoichiometry of H ions Ejection during Respiration-dependent Accumulation of Ca ions by Rat Liver Mitochondria, M.D. Brand, C.-H. Chen, and A. L. Lehninger, J. Biol. Chem., 251:968 (1976).